Endoderm, cardiac and neural inducing factors - xenopus paraxial protocadherin protein

ABSTRACT

Novel proteins have been designated “cerberus” and “frzb-1,” respectively. Cerebus is expressed as a secreted peptide during embryogenesis of the Xenopus embryo, and is expressed specifically in the head organizer region. This new molecule has endodermal, cardiac, and neural tissue inducing activity, that should prove useful in therapeutic, diagnostic, and clinical applications requiring regeneration, differentiation, or repair of these and other tissues. Frzb-1 is a soluble antagonist of growth factors of the Wnt family that acts by binding to Wnt growth factors in the extracellular space. A third novel protein is therm PAPC which promotes the formation of dorsal mesoderm and somites in the embryo.

[0001] This application claims the benefit of U.S. Provisional Application No. 60/020,150, filed Jun. 20, 1996.

[0002] This invention was made with Government support under grant contract number HD-21502, awarded by the National Institutes of Health. The Government has certain rights in this invention.

FIELD OF THE INVENTION

[0003] The invention generally relates to growth factors, neurotrophic factors, and their inhibitors, and more particularly to several new growth factors with neural, endodermal, and cardiac tissue inducing activity, to complexes and compositions including the factors, and to DNA or RNA coding sequences for the factors. Further, one of the novel growth factors should be useful in tumor suppression gene therapy.

BACKGROUND OF THE INVENTION

[0004] Growth factors are substances, such as polypeptide hormones, which affect the growth of defined populations of animal cells in vivo or in vitro, but which are not nutrient substances. Proteins involved in the growth and differentiation of tissues may promote or inhibit growth, and promote or inhibit differentiation, and thus the general term “growth factor” includes cytokines, trophic factors, and their inhibitors.

[0005] Widespread neuronal cell death accompanies normal development of the central and peripheral nervous systems. Studies of peripheral target tissues during development have shown that neuronal cell death results from the competition among neurons for limiting amounts of survivor factors (“neurotrophic factors”). The earliest identified of these, nerve growth factor (“NGF”), is the most fully characterized and has been shown to be essential for the survival of sympathetic and neural crest-derived sensory neurons during early development of both chick and rat.

[0006] One family of neurotropic factors are the Wnts, which have dorsal axis-inducing activity. Most of the Wnt proteins are bound to cell surfaces. (See, e.g., Sokol et al., Science, 249, pp. 561-564, 1990.) Dorsal axis-inducing activity in Xenopus embryos by one member of this family (Xwnt-8) was described by Smith and Harland in 1991, Cell, 67, pp. 753-765. The authors described using RNA injections as a strategy for identifying endogenous RNAS involved in dorsal patterning to rescue dorsal development in embryos that were ventralized by UV irradiation.

[0007] Another member of the growth and neurotropic factor family was subsequently discovered and described by Harland and Smith, which they termed “noggin.” (Cell, 70, pp. 829-840 (1992).) Noggin is a good candidate to function as a signaling molecule in Nieuwkoop's center, by virtue of its maternal transcripts, and in Spemann's organizer, through its zygotic organizer-specific expression. Besides noggin, other secreted factors may be involved in the organizer phenomenon.

[0008] Another Xenopus gene designated “chordin” that begins to be expressed in Spemann's organizer and that can completely rescue axial development in ventralized embryos was described by Sasai et al., Cell, 79, pp. 779-790, 1994. In addition to dorsalizing mesoderm, chordin has the ability to induce neural tissue and its activities are antagonized by Bone Morphogenetic Protein-4 (Sasai et al., Nature, 376, pp. 333-336, 1995).

[0009] Therefore, the dorsal lip or Spemann's organizer of the Xenopus embryo is an ideal tissue for seeking novel growth and neurotrophic factors. New growth and neurotrophic factors are useful agents, particularly those that are secreted due to their ability to be used in physiologically active, soluble forms because these factors, their receptors, and DNA or RNA coding sequences therefore and fragments thereof are useful in a number of therapeutic, clinical, research, diagnostic, and drug design applications.

SUMMARY OF THE INVENTION

[0010] In one aspect of the present invention, the sequence of the novel peptide that can be in substantially purified form is shown by SEQ ID NO:1. The Xenopus derived SEQ ID NO:1 has been designated “cerberus,” and this peptide is capable of inducing endodermal, cardiac, and neural tissue development in vertebrates when expressed. The nucleotide sequence which, when expressed results in cerberus, is illustrated by SEQ ID NO:2. Since peptides of the invention induce endodermal, cardiac, and neural tissue differentiation in vertebrates, they should be able to be prepared in physiologically active form for a number of therapeutic, clinical, and diagnostic applications.

[0011] Cerberus was isolated during a search for molecules expressed specifically in Spemann's organizer containing a secretory signal sequence. In addition to cerberus, two other novel cDNAs were identified.

[0012] The Xenopus derived peptide that can be deduced from SEQ ID NO:3 encodes a novel protein we had earlier designated as “frazzled,” a secreted protein of 318 amino acids that has dorsalizing activity in Xenopus embryos. We now designate the novel protein as “frzb-1.” The gene for frzb-1 is expressed in many adult tissues of many animals, three of the cDNAs (Xenopus, mouse, and human) have been cloned by us. The accession numbers for the Xenopus, mouse, and human frzb-1 cDNA sequences of the gene now designated frzb-1 are U68059, U68058, and U68057, respectively. Frzb-1 has some degree of sequence similarity to the Drosophila gene frizzled which has been shown to encode a seven-transmembrane protein that can act both as a signalling and as a receptor protein (Vinson et al., Nature, 338, pp. 263-264, 1989; Vinson and Adler, Nature, 329, pp. 549-551, 1987). Vertebrate homologues of Frizzled have been isolated and they too were found to be anchored to the cell membrane by seven membrane spanning domains (Wang et al., J. Biol. Chem., 271, pp. 4468-4476, 1996). Frzb-1 differs from the frizzled proteins in that it is an entirely soluble, diffusible secreted protein and therefore suitable as a therapeutic agent. The nucleotide sequence derived from Xenopus that, when expressed, results in frzb-1 protein is illustrated by SEQ ID NO:4. The frzb-1 protein derived from mouse is shown as SEQ ID NO:7, while the mouse frzb-1 nucleotide sequence is SEQ ID NO:8. The human derived frzb-1 protein is illustrated by SEQ ID NO:9, and the human frzb-1 nucleotide sequence is SEQ ID NO:10.

[0013] Frzb-1 is an antagonist of Wnts in vivo, and thus is believed to find utility as a tumor suppressor gene, since overexpressed Wnt proteins cause cancer. Frzb-1 may also be a useful vehicle for solubilization and therapeutic delivery of Wnt proteins complexed with it.

[0014] The final cDNA isolated containing a signal sequence results in a peptide designated Paraxial Protocadherin (PAPC). The cDNA for PAPC is a divergent member of the cadherin multigene family. PAPC is most related to protocadherin 43 reported by Sano et al., The EMBO J., 12, pp. 2249-2256, 1993. As shown in SEQ ID NO:5, the PAPC gene encodes a transmembrane protein of 896 amino acids, of which 187 are part of an intracellular domain. PAPC is a cell adhesion molecule, and microinjection of PAPC mRNA constructs into Xenopus embryos suggest that PAPC acts as a molecule involved in mesoderm differentiation. A soluble form of the PAPC extracellular domain is able to block muscle and mesoderm formation in Xenopus embryos. The nucleotide sequence encoding Xenopus PAPC is provided in SEQ ID NO:6.

[0015] Cerberus, frzb-1, or PAPC or fragments thereof (which also may be synthesized by in vitro methods) may be fused (by recombinant expression or in vitro covalent methods) to an immunogenic polypeptide and this, in turn, may be used to immunize an animal in order to raise antibodies against the novel proteins. Antibodies are recoverable from the serum of immunized animals. Alternatively, monoclonal antibodies may be prepared from cells from the immunized animal in conventional fashion. Immobilized antibodies are useful particularly in the diagnosis (in vitro or in vivo) or purification of cerberus, frzb-1, or PAPC.

[0016] Substitutional, deletional, or insertional mutants of the novel polypeptides may be prepared by in vitro or recombinant methods and screened for immuno-crossreactivity with cerberus, frzb-1, or PAPC and for cerberus antagonist or agonist activity.

[0017] Cerberus or frzb-1 also may be derivatized in vitro in order to prepare immobilized and labelled proteins, particularly for purposes of diagnosis of insufficiencies thereof, or for affinity purification of antibodies thereto.

[0018] Among applications for the novel proteins are tissue replacement therapy and, because frzb-1 is an antagonist of Wnt signaling, tumor suppression therapies. The cerberus receptor may define a novel signalling pathway. In addition, frzb-1 could permit the isolation of novel members of the Wnt family of growth factors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 illustrates the amino acid sequence (SEQ ID NO:1) of the FIG. 2 cDNA clone for cerberus;

[0020]FIG. 2 illustrates a cDNA clone (SEQ ID NO:2) for cerberus derived from Xenopus. Sense strand is on top (5′ to 3′ direction) and the antisense strand on the bottom line (in the opposite direction);

[0021]FIGS. 3 and 4 show the amino acid and nucleotide sequence, respectively, of full-length frzb-1 from Xenopus (SEQ ID NOS:3 and 4);

[0022]FIGS. 5 and 6 show the amino acid and nucleotide sequence, respectively, of full-length PAPC from Xenopus (SEQ ID NOS:5 and 6);

[0023]FIGS. 7 and 8 show the amino acid and nucleotide sequence, respectively, of full-length frzb-1 from mouse (SEQ ID NOS:7 and 8); and

[0024]FIGS. 9 and 10 show the amino acid and nucleotide sequence, respectively, of full-length frzb-1 from human (SEQ ID NOS:9 and 10).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Among the several novel proteins and their nucleotide sequences described herein, is a novel endodermal, cardiac, and neural inducing factor in vertebrates that we have named “cerberus.” When referring to cerberus, the present invention also contemplates the use of fragments, derivatives, agonists, or antagonists of cerberus molecules. Because cerberus has no homology to any reported growth factors, it is proposed to be the founding member of a novel family of growth factors with potent biological activities, which may be isolated using SEQ ID NO:2.

[0026] The amphibian organizer consists of several cell populations with region-specific inducing activities. On the basis of morphogenetic movements, three very different cell populations can be distinguished in the organizer. First, cells with crawling migration movements involute, fanning out to form the prechordal plate. Second, cells involute through the dorsal lip driven by convergence and extension movements, giving rise to the notochord of the trunk. Third, involution ceases and the continuation of mediolateral intercalation movements leads to posterior extension movements and to the formation of the tail notochord and of the chordoneural hinge. The three cell populations correspond to the head, trunk, and tail organizers, respectively.

[0027] The cerberus gene is expressed at the right time and place to participate in cell signalling by Spemann's organizer. Specifically, cerberus is expressed in the head organizing region that consists of crawling-migrating cells. The cerberus expressing region corresponds to the prospective foregut, including the liver and pancreas anlage, and the heart mesoderm. Cerberus expression is activated by chordin, noggin, and organizer-specific homeobox genes.

[0028] Our studies were conducted in early embryos of the frog Xenopus laevis. The frog embryo is well suited to experiments, particularly experiments pertaining to generating and maintaining regional differences within the embryo for determining roles in tissue differentiation. It is easy to culture embryos with access to the embryos even at very early stages of development (preceding and during the formation of body pattern and differentiation) and the embryos are large. The initial work with noggin and chordin also had been in Xenopus embryos, and, as predicted, was highly conserved among vertebrates. Predictions based on work with Xenopus as to corresponding human noggin were proven true and the ability to clone the gene for human noggin was readily accomplished. (See the description of Xenopus work and cloning information in PCT application, published Mar. 17, 1994, WO 9 405 800, and the subsequent human cloning based thereon in the PCT application, also published Mar. 17, 1994, as WO 9 405 791.)

Cloning

[0029] The cloning of cerberus, frzb-1, and PAPC resulted from a comprehensive screen for cDNAs enriched in Spemann's organizer. Subtractive differential screening was performed as follows. In brief, poly A⁺ RNA was isolated from 300 dorsal lip and ventral marginal zone (VMZ) explants at stage 10½. After first strand cDNA synthesis approximately 70-80% of common sequences were removed by substraction with biotinylated VMZ poly A⁺ RNA prepared from 1500 ventral gastrula halves. For differential screening, duplicate filters (2000 plaques per 15 cm plate, a total of 80,000 clones screened) of an unamplified oriented dorsal lip library were hybridized with radiolabeled dorsal lip or VMZ cDNA. Putative organizer-specific clones were isolated, grouped by sequence analysis from the 5′ end and whole-mount in situ hybridization, and subsequently classified into known and new dorsal-specific genes. Rescreening of the library (100,000 independent phages) with a cerberus probe resulted in the isolation of 45 additional clones, 31 of which had similar size as the longest one of the 11 original clones indicating that they were presumably full-length cDNAs. The longest cDNAS for cerberus, frzb-1, and PAPC were completely sequenced.

[0030] To explore the molecular complexity of Spemann's organizer we performed a comprehensive differential screen for dorsal-specific cDNAS. The method was designed to identify abundant cDNAs without bias as to their function. As shown in Table 1, five previously known cDNAs and five new ones were isolated, of which three (expressed as cerberus, frzb-1, and PAPC, respectively) had secretory signal sequences. TABLE 1 Gene Product No. of Isolates Previously Known Genes Chordin novel secreted protein 70 Goosecoid homeobox gene 3 Pintallavis/XFKH-1 forkhead/transcription factor 2 Xnot-2 homeobox gene 1 Xlim-1 homeobox gene 1 New Genes Cerberus novel secreted protein 11 PAPC cadherin-like/transmembrane 2 Frzb-1 novel secreted protein 1 Sox-2 sry/transcription factor 1 Fkh-like forkhead/transcription factor 1

[0031] The most abundant dorsal-specific cDNA was chordin (chd), with 70 independent isolates. The second most abundant cDNA was isolated 11 times and named cerberus (after a mythological guardian dog with multiple heads). The cerberus cDNA encodes a putative secreted polypeptide of 270 amino acids, with an amino terminal hydrophobic signal sequence and a carboxy terminal cysteine-rich region (FIG. 1). Cerberus is expressed specifically in the head organizer region of the Xenopus embryo, including the future foregut.

[0032] An abundant mRNA found in the dorsal region of the Xenopus gastrula encodes the novel putative secreted protein we have designated as cerberus. Cerberus mRNA has potent inducing activity in xenopus embryos, leading to the formation of ectopic heads. Unlike other organizer-specific factors, cerberus does not dorsalize mesoderm and is instead an inhibitor of trunk-tail mesoderm. Cerberus is expressed in the anterior-most domain of the gastrula including the leading edge of the deep layer of the dorsal lip a region that, as shown here, gives rise to foregut and midgut endoderm. Cerberus promotes the formation of cement gland, olfactory placodes, cyclopic eyes, forebrain, and duplicated heart and liver (a foregut derivative). Because the pancreas is also derived from this foregut region, it is likely that cerberus induces pancreas in addition to liver. The expression pattern and inducing activities of cerberus suggest a role for a previously neglected region of the embryo, the prospective foregut endoderm, in the induction of the anterior head region of the embryo.

[0033] Turning to FIG. 1, Xenopus cerberus encodes a putative secreted protein transiently expressed during embryogenesis and the deduced amino acid sequence of Xenopus cerberus is shown. The signal peptide sequence and the nine cysteine residues in the carboxy-terminus are indicated in bold. Potential N-linked glycosylation sites are underlined. In database searches the cerberus protein showed limited similarity only to the mammalian Dan protein, a possible tumor suppressor proposed to be a DNA-binding protein.

[0034] Cerberus appears to be a pioneer protein, as its amino acid sequence and the spacing of its 9 cysteine residues were not significantly similar to other proteins in the databases (NCBI-Gen Bank release 93.0). We conclude that the second most abundant dorsal-specific cDNA encodes a novel putative secreted factor, which should be the founding member of a novel family of growth factors active in cell differentiation.

[0035] Cerberus Demarcates an Anterior Organizer Domain. Cerberus mRNA is expressed at low levels in the unfertilized egg, and zygotic transcripts start accumulating at early gastrula. Expression continues during gastrula and early neurula, rapidly declining during neurulation. Importantly, cerberus expression starts about one hour after that of chd, suggesting that cerberus could act downstream of the chd signal.

[0036] Whole-mount in situ hybridizations reveal that expression starts in the yolky endomesodermal cells located in the deep layer of the organizer. The cerberus domain includes the leading edge of the most anterior organizer cells and extends into the lateral mesoderm. The leading edge gives rise to liver, pancreas, and foregut in its midline, and the more lateral region gives rise to heart mesoderm at later stages of development.

[0037]FIG. 2 sets out the sequence of a full length Xenopus cDNA for cerberus.

[0038] This entirely new molecule has demonstrated physiological properties that should prove useful in therapeutic, diagnostic, and clinical applications that require regeneration, differentiation, or repair of tissues, such wound repair, neuronal regenerational or transplantation, supplementation of heart muscle differentiation, differentiation of pancreas and liver, and other applications in which cell differentiation processes are to be induced.

[0039] The second, novel, secreted protein we have discovered is called “frzb-1,” which was shown to be a secreted protein in Xenopus oocyte microinjection experiments. Thus it provides a natural soluble form of the related extracellular domains of Drosophila and vertebrate frizzled proteins. We propose that the latter proteins could be converted into active soluble forms by introducing a stop codon before the first transmembrane domain. We have noted that the cysteine-rich region of frzb-1 and frizzled contains some overall structural homology with Wnt proteins using the Profile Search homology program (Gribskov, Meth. Enzymol., 183, pp. 146-159, 1990). This had raised the interesting possibility that frzb-1 could interact directly with Wnt growth factors in the extracellular space. This was because we had found that when microinjected into Xenopus embryos, frzb-1 constructs have moderate dorsalizing activity, leading to the formation of embryos with enlarged brain and head, and shortened truck. Somatic muscle differentiation, which requires Xwnt-8, was inhibited. In the case of frzb-1, an attractive hypothesis, suggested by the structural homologies, was that it may act as an inhibitor of Wnt-8, a growth factor that has ventralizing activity in the Xenopus embryo (Christian and Moon, Genes Dev., 7, pp. 13-28, 1993). We have shown that frzb-1 can interact with Xwnt-8 and Wnt-1, and it is expected that it could also interact with other members of the Wnt family of growth factors, of which at least 15 members exist in mammals. In addition, a possible interaction with Wnts was suggested by the recent discovery that dishevelled, a gene acting downstream of wingless, has strong genetic interaction with frizzled mutants in Drosophila (Krasnow et al., Development, 121, pp. 4095-4102, 1995). This possibility has been explored in depth (Leyns et al., Cell, 88, pp. 747-756, Mar. 21, 1997), because a soluble antagonist of the Wnt family of proteins is expected to be of great therapeutic value. Examples 1 and 2 illustrate tests that show antagonism of Xwnt-8 by binding to frzb-1.

[0040] Vertebrate homologues of Frizzled have been isolated and they too are anchored to the cell membrane by seven membrane spanning domains (Wang et al., J. Biol. Chem., 271, pp. 4468-4476, 1996). Frzb-1 differs from the frizzled proteins in that it is an entirely soluble, diffusible secreted protein and therefore suitable as a therapeutic agent. The nucleotide sequence that when expressed results in frzb-1 protein is illustrated by SEQ ID NO:4.

[0041] SEQ ID NO:4 corresponds to the Xenopus homolog, but by using it in BLAST searches (and by cloning mouse frzb-1) we had been able to assemble the sequence of the entire mature human frzb-1 protein, SEQ ID NO:9. Indeed, human frzb-1 is encoded in six expressed sequence tags (ESTS) available in Genebank. The human frzb-1 sequence can be assembled by overlapping in the 5′ to 3′ direction the ESTs with the following accession numbers in Genebank: H18848, R63748, W38677, W44760, H38379, and N71244. No function had yet been assigned to these EST sequences, but we believe and thus propose here that human frzb-1 will have similar functions in cell differentiation to those described above for Xenopus frzb-1. The nucleotide sequence of human frzb-1 is shown in SEQ ID NO:10. The mouse frzb-1 protein and nucleotide sequences are provided by SEQ ID NOS:7 and 8, respectively.

[0042] In particular, we believe that frzb-1 will prove useful in gene therapy of human cancer cells. In this rapidly developing field, one approach is to introduce vectors expressing anti-sense sequences to block expression of dominant ocogenes and growth factor receptors. Another approach is to produce episomal vectors that will replicate in human cells in a controlled fashion without transforming the cells. For an example of the latter (an episomal expression vector system for human gene therapy), reference is made to U.S. Pat. No. 5,624,820, issued Apr. 29, 1997, inventor Cooper.

[0043] Gene therapy now includes uses of human tumor suppression genes. For example, U.S. Pat. No. 5,491,064, issued Feb. 13, 1996, discloses a tumor suppression gene localized on chromosome 11 and described as potentially useful for gene therapy in cancers deleted or altered in their expression of that gene. Frzb-1 maps to chromosome 2q31-33 and loss of one copy of the 2q31-33 and loss of one copy of the 2q arm has been observed with high incidence in lung carcinomas, colo-rectal carcinomas, and neuroblastomas, which has lead to the proposal that the 2q arm carries a tumor suppressor gene. We expect frzb to be a tumor suppressor gene, and thus to be useful in tumor suppression applications.

[0044] A number of applications for cerberus and frzb-1 are suggested from their pharmacological (biological activity) properties.

[0045] For example, the cerberus and frzb-1 cDNAs should be useful as a diagnostic tool (such as through use of antibodies in assays for proteins in cell lines or use of oligonucleotides as primers in a PCR test to amplify those with sequence similarities to the oligonucleotide primer, and to determine how much of the novel protein is present).

[0046] Cerberus, of course, might act upon its target cells via its own receptor. Cerberus, therefore, provides the key to isolate this receptor. Since many receptors mutate to cellular oncogenes, the cerberus receptor should prove useful as a diagnostic probe for certain tumor types. Thus, when one views cerberus as ligand in complexes, then complexes in accordance with the invention include antibody bound to cerberus, antibody bound to peptides derived from cerberus, cerberus bound to its receptor, or peptides derived from cerberus bound to its receptor or other factors. Mutant forms of cerberus, which are either more potent agonists or antagonists, are believed to be clinically useful. Such complexes of cerberus and its binding protein partners will find uses in a number of applications.

[0047] Practice of this invention includes use of an oligonucleotide construct comprising a sequence coding for cerberus or frzb-1 and for a promoter sequence operatively linked in a mammalian or a viral expression vector. Expression and cloning vectors contain a nucleotide sequence that enables the vector to replicate in one or more selected host cells. Generally, in cloning vectors this sequence is one that enables the vector to replicate independently of the host chromosomes, and includes origins of replication or autonomously replicating sequences. The well-known plasmid pBR322 is suitable for most gram negative bacteria, the 2μ plasmid origin for yeast and various viral origins (SV40, polyoma, adenovirus, VSV or BPV) are useful for cloning vectors in mammalian cells.

[0048] Expression and cloning vectors should contain a selection gene, also termed a selectable marker. Typically, this is a gene that encodes a protein necessary for the survival or growth of a host cell transformed with the vector. The presence of this gene ensures that any host cell which deletes the vector will not obtain an advantage in growth or reproduction over transformed hosts. Typical selection genes encode proteins that (a) confer resistance to antibiotics or other toxins, e.g. ampicillin, neomycin, methotrexate or tetracycline, (b) complement auxotrophic deficiencies.

[0049] Examples of suitable selectable markers for mammalian cells are dihydrofolate reductase (DHFR) or thymidine kinase. Such markers enable the identification of cells which were competent to take up the cerberus nucleic acid. The mammalian cell transformants are placed under selection pressure which only the transformants are uniquely adapted to survive by virtue of having taken up the marker. Selection pressure is imposed by culturing the transformants under conditions in which the concentration of selection agent in the medium is successively changed. Amplification is the process by which genes in greater demand for the production of a protein critical for growth are reiterated in tandem within the chromosomes of successive generations of recombinant cells. Increased quantities of cerberus or frzb-1 can therefor be synthesized from the amplified DNA.

[0050] For example, cells transformed with the DHFR selection gene are first identified by culturing all of the transformants in a culture medium which contains methotrexate (Mtx), a competitive antagonist of DHFR. An appropriate host cell in this case is the Chinese hamster ovary (CHO) cell line deficient in DHFR activity, prepared and propagated as described by Urlaub and Chasin, Proc. Nat. Acac. Sci., 77, 4216 (1980). The transformed cells then are exposed to increased levels of Mtx. This leads to the synthesis of multiple copies of the DHFR gene and, concomitantly, multiple copies of other DNA comprising the expression vectors, such as the DNA encoding cerberus or frzb-1. Alternatively, host cells transformed by an expression vector comprising DNA sequences encoding cerberus or frzb-1 and aminoglycoside 3′ phosphotransferase (APH) protein can be selected by cell growth in medium containing an aminoglycosidic antibiotic such as kanamycin or neomycin or G418. Because eukaryotic cells do not normally express an endogenous APH activity, genes encoding APH protein, commonly referred to as neo resistant genes, may be used as dominant selectable markers in a wide range of eukaryotic host cells, by which cells transformed by the vector can readily be identified.

[0051] Expression vectors, unlike cloning vectors, should contain a promoter which is recognized by the host organism and is operably linked to the cerberus nucleic acid. Promoters are untranslated sequences located upstream from the start codon of a structural gene (generally within about 100 to 1000 bp) that control the transcription and translation of nucleic acid under their control. They typically fall into two classes, inducible and constitutive. Inducible promoters are promoters that initiate increased levels of transcription from DNA under their control in response to some change in culture conditions, e.g. the presence or absence of a nutrient or a change in temperature. At this time a large number of promoters recognized by a variety of potential host cells are well known. These promoters can be operably linked to cerberus encoding DNA by removing them from their gene of origin by restriction enzyme digestion, followed by insertion 5′ to the start codon for cerberus or frzb-1.

[0052] Nucleic acid is operably linked when it is placed into a functional relationship with another nucleic acid sequence. For example, DNA for a presequence or secretory leader is operably linked to DNA for a polypeptide if it is expressed as a preprotein which participates in the secretion of the polypeptide; a promoter or enhancer is operably linked to a coding sequence if it affects the transcription of the sequence; or a ribosome binding site is operably linked to a coding sequence if it is positioned so as to facilitate translation. Generally, operably linked means that the DNA sequences being linked are contiguous and, in the case of a secretory leader, contiguous and in reading phase. Linking is accomplished by ligation at convenient restriction sites. If such sites do not exit then synthetic oligonucleotide adapters or linkers are used in accord with conventional practice.

[0053] Transcription of the protein-encoding DNA in mammalian host cells is controlled by promoters obtained from the genomes of viruses such as polyoma, cytomegalo-virus, adenovirus, retroviruses, hepatitis-B virus, and most preferably Simian Virus 40 (SV40), or from heterologous mammalian promoters, e.g. the actin promoter. Of course, promoters from the host cell or related species also are useful herein.

[0054] Cerberus and frzb-1 are clearly useful as a component of culture media for use in culturing cells, such as endodermal, cardiac, and nerve cells, in vitro. We believe cerberus and frzb-1 will find uses as agents for enhancing the survival or inducing the growth of liver, pancreas, heart, and nerve cells, such as in tissue replacement therapy.

[0055] The final cDNA isolated containing a signal sequence results in a peptide designated Paraxial Protocadherin (PAPC). The cDNA for PAPC is a divergent member of the cadherin multigene family. PAPC is most related to protocadherin 43 reported by Sano et al., The EMBO J., 12, pp. 2249-2256, 1993. As shown in SEQ ID NO:5, the PAPC gene encodes a transmembrane protein of 896 amino acids, of which 187 are part of an intracellular domain. PAPC is a cell adhesion molecule, and microinjection of PAPC mRNA constructs into Xenopus embryos suggest that PAPC acts in mesoderm differentiation. The nucleotide sequence encoding Xenopus PAPC is provided in SEQ ID NO:6.

[0056] Therapeutic formulations of the novel proteins may be prepared for storage by mixing the polypeptides having the desired degree of purity with optional physiologically acceptable carriers, excipients or stabilizers, in the form of lyophilized cake or aqueous solutions. Acceptable carriers, excipients or stabilizers are nontoxic to recipients at the dosages and concentrations employed, and include buffers such as phosphate, citrate, and other organic acids; anti-oxidants including ascorbic acid; low molecular weight (less than about 10 residues) polypeptides; proteins, such as serum albumin, gelatin or immunoglobulins. Other components can include glycine, blutamine, asparagine, arginine, or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugar alcohols such as mannitol or sorbitol; salt-forming counterions such as sodium; and/or nonionic surfactants such as Tween, Pluronics or PEG.

[0057] Polyclonal antibodies to the novel proteins generally are raised in animals by multiple subcutaneous (sc) or intraperitoneal (ip) injections of cerberus or frzb-1 and an adjuvant. It may be useful to conjugate these proteins or a fragment containing the target amino acid sequence to a protein which is immunogenic in the species to be immunized, e.g., keyhole limpet hemocyanin, serum albumin, bovine thyroglobulin, or soybean trypsin inhibitor using a bifunctional or derivatizing agent, for example, maleimidobenzoyl sulfosuccinimide ester (conjugation through cysteine residues), N-hydroxysuccinimide (through lysine residues), glutaraldehyde, succinic anhydride, SOCl₂, or R¹IN═C═NR.

[0058] Animals can be immunized against the immunogenic conjugates or derivatives by combining 1 mg or 1 μg of conjugate (for rabbits or mice, respectively) with 3 volumes of Freund's complete adjuvant and injecting the solution intradermally in multiple sites. One month later the animals are boosted with ⅕ to {fraction (1/10)} the original amount of conjugate in Fruend's complete adjuvant by subcutaneous injection at multiple sites. Seven to 14 days later animals are bled and the serum is assayed for anti-cerberus titer. Animals are boosted until the titer plateaus. Preferably, the animal is boosted with the conjugate of the same cerberus or frzb-1 polypeptide, but conjugated to a different protein and/or through a different cross-linking agent. Conjugates also can be made in recombinant cell culture as protein fusions. Also, aggregating agents such as alum are used to enhance the immune response.

[0059] Monoclonal antibodies are prepared by recovering spleen cells from immunized animals and immortalizing the cells in conventional fashion, e.g. by fusion with myeloma cells or by EB virus transformation and screening for clones expressing the desired antibody.

[0060] Antibodies are useful in diagnostic assays for cerberus, frzb-1, or PAPC or their antibodies and to identify family members. In one embodiment of a receptor binding assay, an antibody composition which binds to all of a selected plurality of members of the cerberus family is immobilized on an insoluble matrix, the test sample is contacted with the immobilized antibody composition in order to adsorb all cerberus family members, and then the immobilized family members are contacted with a plurality of antibodies specific for each member, each of the antibodies being individually identifiable as specific for a predetermined family member, as by unique labels such as discrete fluorophores or the like. By determining the presence and/or amount of each unique label, the relative proportion and amount of each family member can be determined.

[0061] The antibodies also are useful for the affinity purification of the novel proteins from recombinant cell culture or natural sources. Antibodies that do not detectably cross-react with other growth factors can be used to purify the proteins free from these other family members.

EXAMPLE 1 Frzb-1 Antagonizes Xwnt-8 Non-Cell Autonomously

[0062] To test whether frzb-1 can antagonize secondary axes caused by Xwnt-8 after secretion by injected cells, an experimental design was used. Thus, frzb-1 mRNA was injected into each of the four animal blastomeres of eight-cell embryos, and subsequently, a single injection of Xwnt-8 mRNA was given to a vegetal-ventral blastomere at the 16-32 cell stage. In two independent experiments, we found that injection of frzb-1 alone (n=13) caused mild dorsalization with enlargement of the cement gland in all embryos and that injection of Xwnt-8 alone (n=53) lead to induction of complete secondary axes in 67% of the embryos. However, injection of frzb-1 into animal caps abolished the formation of complete axes induced by Xwnt-8 (n=27), leaving only a residual 14% of embryos with very weak secondary axes. The double-injected embryos retained the enlarged cement gland phenotype caused by injection of frzb-1 mRNA alone. Because both mRNAs encode secreted proteins and were microinjected into different cells, we conclude that the antagonistic effects of frzb-1 and Xwnt-8 took place in the extracellular space after these proteins were secreted.

EXAMPLE 2 Membrane-Anchored Wnt-1 Confers Frzb-1 Binding

[0063] To investigate a possible interaction between frzb-1 and Wnts, the first step was to insert an HA epitope tag into a Xenopus frzb-1 construct driven by the CMV (cytomegalovirus) promoter. Frzb1-HA was tested in mRNA microinjection assays in Xenopus embryos and found to be biologically active. Conditioned medium from transiently transfected cells contained up to 10 μg/ml of Frzb1-HA (quantitated on Western blots using an HA-tagged protein standard).

[0064] Transient transfection of 293 cells has been instrumental in demonstrating interactions between wingless and frizzled proteins. We therefore took advantage of constructs in which Wnt-1 was fused at the amino terminus of CD8, generating a transmembrane protein containing biologically active Wnt-1 exposed to the extracellular compartment. A Wnt1CD8 cDNA construct (a generous gift of Dr. H. Varmus, NIH) was subcloned into the pcDNA (Invitrogen) vector and transfected into 293 cells. After incubation with Frzb1-HA-conditioned medium (overnight at 37° C.), intensely labeled cells were observed by immunofluorescence. As a negative control, a construct containing 120 amino acids of Xenopus chordin, an unrelated secreted protein was used. Transfection of this construct produced background binding of Frzb1l-HA to the extracellular matrix, both uniform and punctate. Cotransfection of Wnt1CD8 with pcDNA-LacZ showed that transfected cells stained positively for Frzb1-HA and LacZ. Since Wnt1CD8 contains the entire CD8 molecule, a CD8 cDNA was used as an additional negative control. After transfection with Lacz and full-length CE8, Frzb1-HA failed to bind to the transfected cells. Although most of our experiments were carried out at 37° C., Frzb1-HA-conditioned medium also stained Wnt1CD8-transfected cells after incubation at 4° C. for 2 hours.

[0065] Attempts to biochemically quantitate the binding of Frzb-1 to Wnt1CD8-transfected cells were unsuccessful due to high background binding to control cultures, presumably due to binding to the extracellular matrix. Thus, we were unable to estimate a K_(D) for the affinity of the Frzb-1/Wnt-1 interaction. However, when serial dilutions of conditioned medium containing Frzb1-HA were performed (ranging from 2.5×10⁻⁷ to 1.25×10⁻¹⁰ M), staining of Wnt1CD8-transfected cells was found at all concentrations.

[0066] Although we have been unable to provide biochemical evidence for direct binding between Wnts and frzb-1, this cell biological assay indicates that Frzb1-HA can bind, directly or indirectly, to Wnt-1 on the cell membrane in the 10⁻¹⁰ M range.

[0067] It is to be understood that while the invention has been described above in conjunction with preferred specific embodiments, the description and examples are intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims.

1 10 1 270 PRT Xenopus 1 Met Leu Leu Asn Val Leu Arg Ile Cys Ile Ile Val Cys Leu Val Asn 1 5 10 15 Asp Gly Ala Gly Lys His Ser Glu Gly Arg Glu Arg Thr Lys Thr Tyr 20 25 30 Ser Leu Asn Ser Arg Gly Tyr Phe Arg Lys Glu Arg Gly Ala Arg Arg 35 40 45 Ser Lys Ile Leu Leu Val Asn Thr Lys Gly Leu Asp Glu Pro His Ile 50 55 60 Gly His Gly Asp Phe Gly Leu Val Ala Glu Leu Phe Asp Ser Thr Arg 65 70 75 80 Thr His Thr Asn Arg Lys Glu Pro Asp Met Asn Lys Val Lys Leu Phe 85 90 95 Ser Thr Val Ala His Gly Asn Lys Ser Ala Arg Arg Lys Ala Tyr Asn 100 105 110 Gly Ser Arg Arg Asn Ile Phe Ser Arg Arg Ser Phe Asp Lys Arg Asn 115 120 125 Thr Glu Val Thr Glu Lys Pro Gly Ala Lys Met Phe Trp Asn Asn Phe 130 135 140 Leu Val Lys Met Asn Gly Ala Pro Gln Asn Thr Ser His Gly Ser Lys 145 150 155 160 Ala Gln Glu Ile Met Lys Glu Ala Cys Lys Thr Leu Pro Phe Thr Gln 165 170 175 Asn Ile Val His Glu Asn Cys Asp Arg Met Val Ile Gln Asn Asn Leu 180 185 190 Cys Phe Gly Lys Cys Ile Ser Leu His Val Pro Asn Gln Gln Asp Arg 195 200 205 Arg Asn Thr Cys Ser His Cys Leu Pro Ser Lys Phe Thr Leu Asn His 210 215 220 Leu Thr Leu Asn Cys Thr Gly Ser Lys Asn Val Val Lys Val Val Met 225 230 235 240 Met Val Glu Glu Cys Thr Cys Glu Ala His Lys Ser Asn Phe His Gln 245 250 255 Thr Ala Gln Phe Asn Met Asp Thr Ser Thr Thr Leu His His 260 265 270 2 1411 DNA Xenopus 2 gaattcctaa aagcggcaca gtgcaggaac agcaagtcgc tcagaaacac tgcagggtct 60 agatatcata caatgttact aaatgtactc aggatctgta ttatcgtctg ccttgtgaat 120 gatggagcag gaaaacactc agaaggacga gaaaggacaa aaacatattc acttaacagc 180 agaggttact tcagaaaaga aagaggagca cgtaggagca agattctgct ggtgaatact 240 aaaggtcttg atgaacccca cattgggcat ggtgattttg gcttagtagc tgaactattt 300 gattccacca gaacacatac aaacagaaaa gagccagaca tgaacaaagt caagcttttc 360 tcaacagttg cccatggaaa caaaagtgca agaagaaaag cttacaatgg ttctagaagg 420 aatatttttt ctcgccgttc ttttgataaa agaaatacag aggttactga aaagcctggt 480 gccaagatgt tctggaacaa ttttttggtt aaaatgaatg gagccccaca gaatacaagc 540 catggcagta aagcacagga aataatgaaa gaagcttgca aaaccttgcc cttcactcag 600 aatattgtac atgaaaactg tgacaggatg gtgatacaga acaatctgtg ctttggtaaa 660 tgcatctctc tccatgttcc aaatcagcaa gatcgacgaa atacttgttc ccattgcttg 720 ccgtccaaat ttaccctgaa ccacctgacg ctgaattgta ctggatctaa gaatgtagta 780 aaggttgtca tgatggtaga ggaatgcacg tgtgaagctc ataagagcaa cttccaccaa 840 actgcacagt ttaacatgga tacatctact accctgcacc attaaaagga ctgtctgcca 900 tacagtatgg aaatgcccat ttgttggaat attcgttaca tgctatgtat ctaaagcatt 960 atgttgcctt ctgtttcata taaccacatg gaataaggat tgtatgaatt ataattaaca 1020 aatggcattt tgtgtaacat gcaagatctc tgttccatca gttgcaagat aaaaggcaat 1080 atttgtttga cttttttcta caaaatgaat acccaaatat atgataagat aatggggtca 1140 aaactgttaa ggggtaatgt aataataggg actaacaacc aatcagcagg tatgatttac 1200 tggtcacctg tttaaaagca aacatcttat tggttgctat gggttactgc ttctgggcaa 1260 aatgtgtgcc tcataggggg gttagtgtgt tgtgtactga attaattgta tttatttcat 1320 tgttacaatg aagaggatgt ctatgtttat ttcactttta ttaatgtaca ataaatgttc 1380 ttgtttcttt aaaaaaaaaa aaaaactcga g 1411 3 318 PRT Xenopus 3 Met Ser Arg Thr Arg Lys Val Asp Ser Leu Leu Leu Leu Ala Ile Pro 1 5 10 15 Gly Leu Ala Leu Leu Leu Leu Pro Asn Ala Tyr Cys Ala Ser Cys Glu 20 25 30 Pro Val Arg Ile Pro Met Cys Lys Ser Met Pro Trp Asn Met Thr Lys 35 40 45 Met Pro Asn His Leu His His Ser Thr Gln Ala Asn Ala Ile Leu Ala 50 55 60 Ile Glu Gln Phe Glu Gly Leu Leu Thr Thr Glu Cys Ser Gln Asp Leu 65 70 75 80 Leu Phe Phe Leu Cys Ala Met Tyr Ala Pro Ile Cys Thr Ile Asp Phe 85 90 95 Gln His Glu Pro Ile Lys Pro Cys Lys Ser Val Cys Glu Arg Ala Arg 100 105 110 Ala Gly Cys Glu Pro Ile Leu Ile Lys Tyr Arg His Thr Trp Pro Glu 115 120 125 Ser Leu Ala Cys Glu Glu Leu Pro Val Tyr Asp Arg Gly Val Cys Ile 130 135 140 Ser Pro Glu Ala Ile Val Thr Val Glu Gln Gly Thr Asp Ser Met Pro 145 150 155 160 Asp Phe Ser Met Asp Ser Asn Asn Gly Asn Cys Gly Ser Gly Arg Glu 165 170 175 His Cys Lys Cys Lys Pro Met Lys Ala Thr Gln Lys Thr Tyr Leu Lys 180 185 190 Asn Asn Tyr Asn Tyr Val Ile Arg Ala Lys Val Lys Glu Val Lys Val 195 200 205 Lys Cys His Asp Ala Thr Ala Ile Val Glu Val Lys Glu Ile Leu Lys 210 215 220 Ser Ser Leu Val Asn Ile Pro Lys Asp Thr Val Thr Leu Tyr Thr Asn 225 230 235 240 Ser Gly Cys Leu Cys Pro Gln Leu Val Ala Asn Glu Glu Tyr Ile Ile 245 250 255 Met Gly Tyr Glu Asp Lys Glu Arg Thr Arg Leu Leu Leu Val Glu Gly 260 265 270 Ser Leu Ala Glu Lys Trp Arg Asp Arg Leu Ala Lys Lys Val Lys Arg 275 280 285 Trp Asp Gln Lys Leu Arg Arg Pro Arg Lys Ser Lys Asp Pro Val Ala 290 295 300 Pro Ile Pro Asn Lys Asn Ser Asn Ser Arg Gln Ala Arg Ser 305 310 315 4 1875 DNA Xenopus 4 gaattccctt tcacacagga ctcctggcag aggtgaatgg ttagccctat ggatttggtt 60 tgttgatttt gacacatgat tgattgcttt cagataggat tgaaggactt ggatttttat 120 ctaattctgc acttttaaat tatctgagta attgttcatt ttgtattgga tgggactaaa 180 gataaactta actccttgct tttgacttgc ccataaacta taaggtgggg tgagttgtag 240 ttgcttttac atgtgcccag attttccctg tattccctgt attccctcta aagtaagcct 300 acacatacag gttgggcaga ataacaatgt ctcgaacaag gaaagtggac tcattactgc 360 tactggccat acctggactg gcgcttctct tattacccaa tgcttactgt gcttcgtgtg 420 agcctgtgcg gatccccatg tgcaaatcta tgccatggaa catgaccaag atgcccaacc 480 atctccacca cagcactcaa gccaatgcca tcctggcaat tgaacagttt gaaggtttgc 540 tgaccactga atgtagccag gaccttttgt tctttctgtg tgccatgtat gcccccattt 600 gtaccatcga tttccagcat gaaccaatta agccttgcaa gtccgtgtgc gaaagggcca 660 gggccggctg tgagcccatt ctcataaagt accggcacac ttggccagag agcctggcat 720 gtgaagagct gcccgtatat gacagaggag tctgcatctc cccagaggct atcgtcacag 780 tggaacaagg aacagattca atgccagact tctccatgga ttcaaacaat ggaaattgcg 840 gaagcggcag ggagcactgt aaatgcaagc ccatgaaggc aacccaaaag acgtatctca 900 agaataatta caattatgta atcagagcaa aagtgaaaga ggtgaaagtg aaatgccacg 960 acgcaacagc aattgtggaa gtaaaggaga ttctcaagtc ttccctagtg aacattccta 1020 aagacacagt gacactgtac accaactcag gctgcttgtg cccccagctt gttgccaatg 1080 aggaatacat aattatgggc tatgaagaca aagagcgtac caggcttcta ctagtggaag 1140 gatccttggc cgaaaaatgg agagatcgtc ttgctaagaa agtcaagcgc tgggatcaaa 1200 agcttcgacg tcccaggaaa agcaaagacc ccgtggctcc aattcccaac aaaaacagca 1260 attccagaca agcgcgtagt tagactaacg gaaaggtgta tggaaactct atggactttg 1320 aaactaagat ttgcattgtt ggaagagcaa aaaagaaatt gcactacagc acgttatatt 1380 ctattgttta ctacaagaag ctggtttagt tgattgtagt tctcctttcc ttcttttttt 1440 ttataactat atttgcacgt gttcccaggc aattgtttta ttcaacttcc agtgacagag 1500 cagtgactga atgtctcagc ctaaagaagc tcaattcatt tctgatcaac taatggtgac 1560 aagtgtttga tacttgggga aagtgaacta attgcaatgg taaatcagag aaaagttgac 1620 caatgttgct tttcctgtag atgaacaagt gagagatcac atttaaatga tgatcacttt 1680 ccatttaata ctttcagcag ttttagttag atgacatgta ggatgcacct aaatctaaat 1740 attttatcat aaatgaagag ctggtttaga ctgtatggtc actgttggga aggtaaatgc 1800 ctactttgtc aattctgttt taaaaattgc ctaaataaat attaagtcct aaataaaaaa 1860 aaaaaaaaaa aaaaa 1875 5 979 PRT Xenopus 5 Met Leu Leu Leu Phe Arg Ala Ile Pro Met Leu Leu Leu Gly Leu Met 1 5 10 15 Val Leu Gln Thr Asp Cys Glu Ile Ala Gln Tyr Tyr Ile Asp Glu Glu 20 25 30 Glu Pro Pro Gly Thr Val Ile Ala Val Leu Ser Gln His Ser Ile Phe 35 40 45 Asn Thr Thr Asp Ile Pro Ala Thr Asn Phe Arg Leu Met Lys Gln Phe 50 55 60 Asn Asn Ser Leu Ile Gly Val Arg Glu Ser Asp Gly Gln Leu Ser Ile 65 70 75 80 Met Glu Arg Ile Asp Arg Glu Gln Ile Cys Arg Gln Ser Leu His Cys 85 90 95 Asn Leu Ala Leu Asp Val Val Ser Phe Ser Lys Gly His Phe Lys Leu 100 105 110 Leu Asn Val Lys Val Glu Val Arg Asp Ile Asn Asp His Ser Pro His 115 120 125 Phe Pro Ser Glu Ile Met His Val Glu Val Ser Glu Ser Ser Ser Val 130 135 140 Gly Thr Arg Ile Pro Leu Glu Ile Ala Ile Asp Glu Asp Val Gly Ser 145 150 155 160 Asn Ser Ile Gln Asn Phe Gln Ile Ser Asn Asn Ser His Phe Ser Ile 165 170 175 Asp Val Leu Thr Arg Ala Asp Gly Val Lys Tyr Ala Asp Leu Val Leu 180 185 190 Met Arg Glu Leu Asp Arg Glu Ile Gln Pro Thr Tyr Ile Met Glu Leu 195 200 205 Leu Ala Met Asp Gly Gly Val Pro Ser Leu Ser Gly Thr Ala Val Val 210 215 220 Asn Ile Arg Val Leu Asp Phe Asn Asp Asn Ser Pro Val Phe Glu Arg 225 230 235 240 Ser Thr Ile Ala Val Asp Leu Val Glu Asp Ala Pro Leu Gly Tyr Leu 245 250 255 Leu Leu Glu Leu His Ala Thr Asp Asp Asp Glu Gly Val Asn Gly Glu 260 265 270 Ile Val Tyr Gly Phe Ser Thr Leu Ala Ser Gln Glu Val Arg Gln Leu 275 280 285 Phe Lys Ile Asn Ser Arg Thr Gly Ser Val Thr Leu Glu Gly Gln Val 290 295 300 Asp Phe Glu Thr Lys Gln Thr Tyr Glu Phe Glu Val Gln Ala Gln Asp 305 310 315 320 Leu Gly Pro Asn Pro Leu Thr Ala Thr Cys Lys Val Thr Val His Ile 325 330 335 Leu Asp Val Asn Asp Asn Thr Pro Ala Ile Thr Ile Thr Pro Leu Thr 340 345 350 Thr Val Asn Ala Gly Val Ala Tyr Ile Pro Glu Thr Ala Thr Lys Glu 355 360 365 Asn Phe Ile Ala Leu Ile Ser Thr Thr Asp Arg Ala Ser Gly Ser Asn 370 375 380 Gly Gln Val Arg Cys Thr Leu Tyr Gly His Glu His Phe Lys Leu Gln 385 390 395 400 Gln Ala Tyr Glu Asp Ser Tyr Met Ile Val Thr Thr Ser Thr Leu Asp 405 410 415 Arg Glu Asn Ile Ala Ala Tyr Ser Leu Thr Val Val Ala Glu Asp Leu 420 425 430 Gly Phe Pro Ser Leu Lys Thr Lys Lys Tyr Tyr Thr Val Lys Val Ser 435 440 445 Asp Glu Asn Asp Asn Ala Pro Val Phe Ser Lys Pro Gln Tyr Glu Ala 450 455 460 Ser Ile Leu Glu Asn Asn Ala Pro Gly Ser Tyr Ile Thr Thr Val Ile 465 470 475 480 Ala Arg Asp Ser Asp Ser Asp Gln Asn Gly Lys Val Asn Tyr Arg Leu 485 490 495 Val Asp Ala Lys Val Met Gly Gln Ser Leu Thr Thr Phe Val Ser Leu 500 505 510 Asp Ala Asp Ser Gly Val Leu Arg Ala Val Arg Ser Leu Asp Tyr Glu 515 520 525 Lys Leu Lys Gln Leu Asp Phe Glu Ile Glu Ala Ala Asp Asn Gly Ile 530 535 540 Pro Gln Leu Ser Thr Arg Val Gln Leu Asn Leu Arg Ile Val Asp Gln 545 550 555 560 Asn Asp Asn Cys Pro Val Ile Thr Asn Pro Leu Leu Asn Asn Gly Ser 565 570 575 Gly Glu Val Leu Leu Pro Ile Ser Ala Pro Gln Asn Tyr Leu Val Phe 580 585 590 Gln Leu Lys Ala Glu Asp Ser Asp Glu Gly His Asn Ser Gln Leu Phe 595 600 605 Tyr Thr Ile Leu Arg Asp Pro Ser Arg Leu Phe Ala Ile Asn Lys Glu 610 615 620 Ser Gly Glu Val Phe Leu Lys Lys Gln Leu Asn Ser Asp His Ser Glu 625 630 635 640 Asp Leu Ser Ile Val Val Ala Val Tyr Asp Leu Gly Arg Pro Ser Leu 645 650 655 Ser Thr Asn Ala Thr Val Lys Phe Ile Leu Thr Asp Ser Phe Pro Ser 660 665 670 Asn Val Glu Val Val Ile Leu Gln Pro Ser Ala Glu Glu Gln His Gln 675 680 685 Ile Asp Met Ser Ile Ile Phe Ile Ala Val Leu Ala Gly Gly Cys Ala 690 695 700 Leu Leu Leu Leu Ala Ile Phe Phe Val Ala Cys Thr Cys Lys Lys Lys 705 710 715 720 Ala Gly Glu Phe Lys Gln Val Pro Glu Gln His Gly Thr Cys Asn Glu 725 730 735 Glu Arg Leu Leu Ser Thr Pro Ser Pro Gln Ser Val Ser Ser Ser Leu 740 745 750 Ser Gln Ser Glu Ser Cys Gln Leu Ser Ile Asn Thr Glu Ser Glu Asn 755 760 765 Cys Ser Val Ser Ser Asn Gln Glu Gln His Gln Gln Thr Gly Ile Lys 770 775 780 His Ser Ile Ser Val Pro Ser Tyr His Thr Ser Gly Trp His Leu Asp 785 790 795 800 Asn Cys Ala Met Ser Ile Ser Gly His Ser His Met Gly His Ile Ser 805 810 815 Thr Lys Asp Ser Gly Lys Gly Asp Ser Asp Phe Asn Asp Ser Asp Ser 820 825 830 Asp Thr Ser Gly Glu Ser Gln Lys Lys Ser Ile Glu Gln Pro Met Gln 835 840 845 Ala Gln Ala Ser Ala Gln Tyr Thr Asp Glu Ser Ala Gly Phe Arg His 850 855 860 Ala Asp Asn Tyr Phe Ser His Arg Ile Asn Lys Gly Pro Glu Asn Gly 865 870 875 880 Asn Cys Thr Leu Gln Tyr Glu Lys Gly Tyr Arg Leu Ser Tyr Ser Val 885 890 895 Ala Pro Ala His Tyr Asn Thr Tyr His Ala Arg Met Pro Asn Leu His 900 905 910 Ile Pro Asn His Thr Leu Arg Asp Pro Tyr Tyr His Ile Asn Asn Pro 915 920 925 Val Ala Asn Arg Met His Ala Glu Tyr Glu Arg Asp Leu Val Asn Arg 930 935 940 Ser Ala Thr Leu Ser Pro Gln Arg Ser Ser Ser Arg Tyr Gln Glu Phe 945 950 955 960 Asn Tyr Ser Pro Gln Ile Ser Arg Gln Leu His Pro Ser Glu Ile Ala 965 970 975 Thr Thr Phe 6 3655 DNA Xenopus 6 gaattcccag agatgaactc cttgagattg ttttaaatga ctgcaggtct ggaaggattc 60 acattgccac actgtttcta ggcatgaaaa aactgcaagt ttcaactttg tttttggtgc 120 aactttgatt cttcaagatg ctgcttctct tcagagccat tccaatgctg ctgttgggac 180 tgatggtttt acaaacagac tgtgaaattg cccagtacta catagatgaa gaagaacccc 240 ctggcactgt aattgcagtg ttgtcacaac actccatatt taacactaca gatatacctg 300 caaccaattt ccgtctaatg aagcaattta ataattccct tatcggagtc cgtgagagtg 360 atgggcagct gagcatcatg gagaggattg accgggagca aatctgcagg cagtcccttc 420 actgcaacct ggctttggat gtggtcagct tttccaaagg acacttcaag cttctgaacg 480 tgaaagtgga ggtgagagac attaatgacc atagccctca ctttcccagt gaaataatgc 540 atgtggaggt gtctgaaagt tcctctgtgg gcaccaggat tcctttagaa attgcaatag 600 atgaagatgt tgggtccaac tccatccaga actttcagat ctcaaataat agccacttca 660 gcattgatgt gctaaccaga gcagatgggg tgaaatatgc agatttagtc ttaatgagag 720 aactggacag ggaaatccag ccaacataca taatggagct actagcaatg gatgggggtg 780 taccatcact atctggtact gcagtggtta acatccgagt cctggacttt aatgataaca 840 gcccagtgtt tgagagaagc accattgctg tggacctagt agaggatgct cctctgggat 900 accttttgtt ggagttacat gctactgacg atgatgaagg agtgaatgga gaaattgttt 960 atggattcag cactttggca tctcaagagg tacgtcagct atttaaaatt aactccagaa 1020 ctggcagtgt tactcttgaa ggccaagttg attttgagac caagcagact tacgaatttg 1080 aggtacaagc ccaagatttg ggccccaacc cactgactgc tacttgtaaa gtaactgttc 1140 atatacttga tgtaaatgat aataccccag ccatcactat tacccctctg actactgtaa 1200 atgcaggagt tgcctatatt ccagaaacag ccacaaagga gaactttata gctctgatca 1260 gcactactga cagagcctct ggatctaatg gacaagttcg ctgtactctt tatggacatg 1320 agcactttaa actacagcaa gcttatgagg acagttacat gatagttacc acctctactt 1380 tagacaggga aaacatagca gcgtactctt tgacagtagt tgcagaagac cttggcttcc 1440 cctcattgaa gaccaaaaag tactacacag tcaaggttag tgatgagaat gacaatgcac 1500 ctgtattttc taaaccccag tatgaagctt ctattctgga aaataatgct ccaggctctt 1560 atataactac agtgatagcc agagactctg atagtgatca aaatggcaaa gtaaattaca 1620 gacttgtgga tgcaaaagtg atgggccagt cactaacaac atttgtttct cttgatgcgg 1680 actctggagt attgagagct gttaggtctt tagactatga aaaacttaaa caactggatt 1740 ttgaaattga agctgcagac aatgggatcc ctcaactctc cactcgcgtt caactaaatc 1800 tcagaatagt tgatcaaaat gataattgcc ctgtgataac taatcctctt cttaataatg 1860 gctcgggtga agttctgctt cccatcagcg ctcctcaaaa ctatttagtt ttccagctca 1920 aagccgagga ttcagatgaa gggcacaact cccagctgtt ctataccata ctgagagatc 1980 caagcagatt gtttgccatt aacaaagaaa gtggtgaagt gttcctgaaa aaacaattaa 2040 actctgacca ttcagaggac ttgagcatag tagttgcagt gtatgacttg ggaagacctt 2100 cattatccac caatgctaca gttaaattca tcctcaccga ctcttttcct tctaacgttg 2160 aagtcgttat tttgcaacca tctgcagaag agcagcacca gatcgatatg tccattatat 2220 tcattgcagt gctggctggt ggttgtgctt tgctactttt ggccatcttt tttgtggcct 2280 gtacttgtaa aaagaaagct ggtgaattta agcaggtacc tgaacaacat ggaacatgca 2340 atgaagaacg cctgttaagc accccatctc cccagtcggt ctcttcttct ttgtctcagt 2400 ctgagtcatg ccaactctcc atcaatactg aatctgagaa ttgcagcgtg tcctctaacc 2460 aagagcagca tcagcaaaca ggcataaagc actccatctc tgtaccatct tatcacacat 2520 ctggttggca cctggacaat tgtgcaatga gcataagtgg acattctcac atggggcaca 2580 ttagtacaaa ggacagtggc aaaggagata gtgacttcaa tgacagtgac tctgatacta 2640 gtggagaatc acaaaagaag agcattgagc agccaatgca ggcacaagcc agtgctcaat 2700 acacagatga atcagcaggg ttccgacatg ccgataacta tttcagccac cgaatcaaca 2760 agggtccaga aaatgggaac tgcacattgc aatatgaaaa gggctataga ctgtcttact 2820 ctgtagctcc tgctcattac aatacctacc atgcaagaat gcctaacctg cacataccga 2880 accataccct tagagaccct tattaccata tcaataatcc tgttgctaat cggatgcacg 2940 cggaatatga aagagattta gtcaacagaa gtgcaacgtt atctccgcag agatcgtcta 3000 gcagatacca agaattcaat tacagtccgc agatatcaag acagcttcat ccttcagaaa 3060 ttgctacaac cttttaatca ttaggcatgc aagtgagaat gcacaaaggc aagtgcttta 3120 gcatgaaagc taaatatatg gagtctcccc tttccctctg atggatgggg ggagacacag 3180 gacagtgcat aaatatacag ctgctttcta tttgcatttc acttgggaat tttttgtttt 3240 ttttacatat ttatttttcc tgaattgaat gtgacattgt cctgtcacct aactagcaat 3300 taaatccaca gacctacagt caaatatttg agggcccctg aaacagcaca tcagtcagga 3360 cctaaagtgg cctttttact tttagcagct cctgggtctg ccctctgtgt taatcagccc 3420 ctggtcaagt cctgagtagg atcatggcgt ttttatatgc atctcaccta ctttggacgt 3480 gatttacaca taataggaaa cgcttggttt cagtgaagtc tgtgttgtat atattctgtt 3540 atatacacgc attttgtgtt tgtgtatata tttcaagtcc attcagatat gtgtatatag 3600 tgcagacctt gtaaattaaa tattctgata ctttttcctc aataaatatt taaat 3655 7 323 PRT Mouse 7 Met Val Cys Cys Gly Pro Gly Arg Met Leu Leu Gly Trp Ala Gly Leu 1 5 10 15 Leu Val Leu Ala Ala Leu Cys Leu Leu Gln Val Pro Gly Ala Gln Ala 20 25 30 Ala Ala Cys Glu Pro Val Arg Ile Pro Leu Cys Lys Ser Leu Pro Trp 35 40 45 Asn Met Thr Lys Met Pro Asn His Leu His His Ser Thr Gln Ala Asn 50 55 60 Ala Ile Leu Ala Met Glu Gln Phe Glu Gly Leu Leu Gly Thr His Cys 65 70 75 80 Ser Pro Asp Leu Leu Phe Phe Leu Cys Ala Met Tyr Ala Pro Ile Cys 85 90 95 Thr Ile Asp Phe Gln His Glu Pro Ile Lys Pro Cys Lys Ser Val Cys 100 105 110 Glu Arg Ala Arg Gln Gly Cys Glu Pro Ile Leu Ile Lys Tyr Arg His 115 120 125 Ser Trp Pro Glu Ser Leu Ala Cys Asp Glu Leu Pro Val Tyr Asp Arg 130 135 140 Gly Val Cys Ile Ser Pro Glu Ala Ile Val Thr Ala Asp Gly Ala Asp 145 150 155 160 Phe Pro Met Asp Ser Ser Thr Gly His Cys Arg Gly Ala Ser Ser Glu 165 170 175 Arg Cys Lys Cys Lys Pro Val Arg Ala Thr Gln Lys Thr Tyr Phe Arg 180 185 190 Asn Asn Tyr Asn Tyr Val Ile Arg Ala Lys Val Lys Glu Val Lys Met 195 200 205 Lys Cys His Asp Val Thr Ala Val Val Glu Val Lys Glu Ile Leu Lys 210 215 220 Ala Ser Leu Val Asn Ile Pro Arg Asp Thr Val Asn Leu Tyr Thr Thr 225 230 235 240 Ser Gly Cys Leu Cys Pro Pro Leu Thr Val Asn Glu Glu Tyr Val Ile 245 250 255 Met Gly Tyr Glu Asp Glu Glu Arg Ser Arg Leu Leu Leu Val Glu Gly 260 265 270 Ser Ile Ala Glu Lys Trp Lys Asp Arg Leu Gly Lys Lys Val Lys Arg 275 280 285 Trp Asp Met Lys Leu Arg His Leu Gly Leu Gly Lys Thr Asp Ala Ser 290 295 300 Asp Ser Thr Gln Asn Gln Lys Ser Gly Arg Asn Ser Asn Pro Arg Pro 305 310 315 320 Ala Arg Ser 8 2176 DNA Mouse 8 aagcctggga ccatggtctg ctgcggcccg ggacggatgc tgctaggatg ggccgggttg 60 ctagtcctgg ctgctctctg cctgctccag gtgcccggag ctcaggctgc agcctgtgag 120 cctgtccgca tcccgctgtg caagtccctt ccctggaaca tgaccaagat gcccaaccac 180 ctgcaccaca gcacccaggc taacgccatc ctggccatgg aacagttcga agggctgctg 240 ggcacccact gcagcccgga tcttctcttc ttcctctgtg caatgtacgc acccatttgc 300 accatcgact tccagcacga gcccatcaag ccctgcaagt ctgtgtgtga gcgcgcccga 360 cagggctgcg agcccattct catcaagtac cgccactcgt ggccggaaag cttggcctgc 420 gacgagctgc cggtgtacga ccgcggcgtg tgcatctctc ctgaggccat cgtcaccgcg 480 gacggagcgg attttcctat ggattcaagt actggacact gcagaggggc aagcagcgaa 540 cgttgcaaat gtaagcctgt cagagctaca cagaagacct atttccggaa caattacaac 600 tatgtcatcc gggctaaagt taaagaggta aagatgaaat gtcatgatgt gaccgccgtt 660 gtggaagtga aggaaattct aaaggcatca ctggtaaaca ttccaaggga caccgtcaat 720 ctttatacca cctctggctg cctctgtcct ccacttactg tcaatgagga atatgtcatc 780 atgggctatg aagacgagga acgttccagg ttactcttgg tagaaggctc tatagctgag 840 aagtggaagg atcggcttgg taagaaagtc aagcgctggg atatgaaact ccgacacctt 900 ggactgggta aaactgatgc tagcgattcc actcagaatc agaagtctgg caggaactct 960 aatccccggc cagcacgcag ctaaatcctg aaatgtaaaa ggccacaccc acggactccc 1020 ttctaagact ggcgctggtg gactaacaaa ggaaaaccgc acagttgtgc tcgtgaccga 1080 ttgtttaccg cagacaccgc gtggctaccg aagttacttc cggtcccctt tctcctgctt 1140 cttaatggcg tggggttaga tcctttaata tgttatatat tctgtttcat caatcacgtg 1200 gggactgttc ttttgcaacc agaatagtaa attaaatatg ttgatgctaa ggtttctgta 1260 ctggactccc tgggtttaat ttggtgttct gtaccctgat tgagaatgca atgtttcatg 1320 taaagagaga atcctggtca tatctcaaga actagatatt gctgtaagac agcctctgct 1380 gctgcgctta tagtcttgtg tttgtatgcc tttgtccatt tccctcatgc tgtgaaagtt 1440 atacatgttt ataaaggtag aacggcattt tgaaatcaga cactgcacaa gcagagtagc 1500 ccaacaccag gaagcattta tgaggaaacg ccacacagca tgacttattt tcaagattgg 1560 caggcagcaa aataaatagt gttgggagcc aagaaaagaa tattttgcct ggttaagggg 1620 cacactggaa tcagtagccc ttgagccatt aacagcagtg ttcttctggc aagtttttga 1680 tttgttcata aatgtattca cgagcattag agatgaactt ataactagac atctgttgtt 1740 atctctatag ctctgcttcc ttctaaatca aacccattgt tggatgctcc ctctccattc 1800 ataaataaat ttggcttgct gtattggcca ggaaaagaaa gtattaaagt atgcatgcat 1860 gtgcaccagg gtgttattta acagaggtat gtaactctat aaaagactat aatttacagg 1920 acacggaaat gtgcacattt gtttactttt tttcttcctt ttgctttggg cttgtgattt 1980 tggtttttgg tgtgtttatg tctgtatttt ggggggtggg taggtttaag ccattgcaca 2040 ttcaagttga actagattag agtagactag gctcattggc ctagacatta tgatttgaat 2100 ttgtgttgtt taatgctcca tcaagatgtc taataaaagg aatatggttg tcaacagaga 2160 cgacaacaac aacaaa 2176 9 325 PRT Human 9 Met Val Cys Gly Ser Pro Gly Gly Met Leu Leu Leu Arg Ala Gly Leu 1 5 10 15 Leu Ala Leu Ala Ala Leu Cys Leu Leu Arg Val Pro Gly Ala Arg Ala 20 25 30 Ala Ala Cys Glu Pro Val Arg Ile Pro Leu Cys Lys Ser Leu Pro Trp 35 40 45 Asn Met Thr Lys Met Pro Asn His Leu His His Ser Thr Gln Ala Asn 50 55 60 Ala Ile Leu Ala Ile Glu Gln Phe Glu Gly Leu Leu Gly Thr His Cys 65 70 75 80 Ser Pro Asp Leu Leu Phe Phe Leu Cys Ala Met Tyr Ala Pro Ile Cys 85 90 95 Thr Ile Asp Phe Gln His Glu Pro Ile Lys Pro Cys Lys Ser Val Cys 100 105 110 Glu Arg Ala Arg Gln Gly Cys Glu Pro Ile Leu Ile Lys Tyr Arg His 115 120 125 Ser Trp Pro Glu Asn Leu Ala Cys Glu Glu Leu Pro Val Tyr Asp Arg 130 135 140 Gly Val Cys Ile Ser Pro Glu Ala Ile Val Thr Ala Asp Gly Ala Asp 145 150 155 160 Phe Pro Met Asp Ser Ser Asn Gly Asn Cys Arg Gly Ala Ser Ser Glu 165 170 175 Arg Cys Lys Cys Lys Pro Ile Arg Ala Thr Gln Lys Thr Tyr Phe Arg 180 185 190 Asn Asn Tyr Asn Tyr Val Ile Arg Ala Lys Val Lys Glu Ile Lys Thr 195 200 205 Lys Cys His Asp Val Thr Ala Val Val Glu Val Lys Glu Ile Leu Lys 210 215 220 Ser Ser Leu Val Asn Ile Pro Arg Asp Thr Val Asn Leu Tyr Thr Ser 225 230 235 240 Ser Gly Cys Leu Cys Pro Pro Leu Asn Val Asn Glu Glu Tyr Ile Ile 245 250 255 Met Gly Tyr Glu Asp Glu Glu Arg Ser Arg Leu Leu Leu Val Glu Gly 260 265 270 Ser Ile Ala Glu Lys Trp Lys Asp Arg Leu Gly Lys Lys Val Lys Arg 275 280 285 Trp Asp Met Lys Leu Arg His Leu Gly Leu Ser Lys Ser Asp Ser Ser 290 295 300 Asn Ser Asp Ser Thr Gln Ser Gln Lys Ser Gly Arg Asn Ser Asn Pro 305 310 315 320 Arg Gln Ala Arg Asn 325 10 1893 DNA Human 10 ggcggagcgg gccttttggc gtccactgcg cggctgcacc ctgccccatc tgccgggatc 60 atggtctgcg gcagcccggg agggatgctg ctgctgcggg ccgggctgct tgccctggct 120 gctctctgcc tgctccgggt gcccggggct cgggctgcag cctgtgagcc cgtccgcatc 180 cccctgtgca agtccctgcc ctggaacatg actaagatgc ccaaccacct gcaccacagc 240 actcaggcca acgccatcct ggccatcgag cagttcgaag gtctgctggg cacccactgc 300 agccccgatc tgctcttctt cctctgtgcc atgtacgcgc ccatctgcac cattgacttc 360 cagcacgagc ccatcaagcc ctgtaagtct gtgtgcgagc gggcccggca gggctgtgag 420 cccatactca tcaagtaccg ccactcgtgg ccggagaacc tggcctgcga ggagctgcca 480 gtgtacgaca ggggcgtgtg catctctccc gaggccatcg ttactgcgga cggagctgat 540 tttcctatgg attctagtaa cggaaactgt agaggggcaa gcagtgaacg ctgtaaatgt 600 aagcctatta gagctacaca gaagacctat ttccggaaca attacaacta tgtcattcgg 660 gctaaagtta aagagataaa gactaagtgc catgatgtga ctgcagtagt ggaggtgaag 720 gagattctaa agtcctctct ggtaaacatt ccacgggaca ctgtcaacct ctataccagc 780 tctggctgcc tctgccctcc acttaatgtt aatgaggaat atatcatcat gggctatgaa 840 gatgaggaac gttccagatt actcttggtg gaaggctcta tagctgagaa gtggaaggat 900 cgactcggta aaaaagttaa gcgctgggat atgaagcttc gtcatcttgg actcagtaaa 960 agtgattcta gcaatagtga ttccactcag agtcagaagt ctggcaggaa ctcgaacccc 1020 cggcaagcac gcaactaaat cccgaaatac aaaaagtaac acagtggact tcctattaag 1080 acttacttgc attgctggac tagcaaagga aaattgcact attgcacatc atattctatt 1140 gtttactata aaaatcatgt gataactgat tattacttct gtttctcttt tggtttctgc 1200 ttctctcttc tctcaacccc tttgtaatgg tttgggggca gactcttaag tatattgtga 1260 gttttctatt tcactaatca tgagaaaaac tgttcttttg caataataat aaattaaaca 1320 tgctgttacc agagcctctt tgctgagtct ccagatgtta atttactttc tgcaccccaa 1380 ttgggaatgc aatattggat gaaaagagag gtttctggta ttcacagaaa gctagatatg 1440 ccttaaaaca tactctgccg atctaattac agccttattt ttgtatgcct tttgggcatt 1500 ctcctcatgc ttagaaagtt ccaaatgttt ataaaggtaa aatggcagtt tgaagtcaaa 1560 tgtcacatag gcaaagcaat caagcaccag gaagtgttta tgaggaaaca acacccaaga 1620 tgaattattt ttgagactgt caggaagtaa aataaatagg agcttaagaa agaacatttt 1680 gcctgattga gaagcacaac tgaaaccagt agccgctggg gtgttaatgg tagcattctt 1740 cttttggcaa tacatttgat ttgttcatga atatattaat cagcattaga gaaatgaatt 1800 ataactagac atctgctgtt atcaccatag ttttgtttaa tttgcttcct tttaaataaa 1860 cccattggtg aaagtcaaaa aaaaaaaaaa aaa 1893 

It is claimed:
 1. A substantially pure protein characterized by a physiologically active form and comprising an amino acid sequence encoded by the DNA of SEQ ID NO:2.
 2. The protein as in claim 1 having neurotrophic, growth or differentiation factor activity.
 3. A composition comprising the protein of claim 1 and a physiologically acceptable carrier with which the peptide is admixed.
 4. An oligonucleotide construct comprising a sequence coding for a protein and an expression vector operatively linked therewith, the protein having neurotrophic, growth or differentiation factor activity and being expressible from SEQ ID NO:2.
 5. The construct as in claim 4 wherein the expression vector is a mammalian or viral expression vector.
 6. A substantially pure protein characterized by a physiologically active form and comprising an amino acid sequence encoded by the DNA of SEQ ID NO:4, SEQ ID NO:8, or SEQ ID NO:10.
 7. The protein as in claim 6 having neurotrophic, growth or differentiation factor activity.
 8. A composition comprising the protein of claim 6 and a physiologically acceptable carrier with which the protein is admixed.
 9. An oligonucleotide construct comprising a sequence coding for a protein and an expression vector operatively linked therewith, the protein being expressible from SEQ ID NO:4, SEQ ID NO:8 or SEQ ID NO:10.
 10. The construct as in claim 9 wherein the protein is expressible in soluble form.
 11. The construct as in claim 9 wherein the expression vector is a mammalian or viral expression vector.
 12. A complex comprising a substantially pure frzb-1 protein complexed with at least one Wnt protein.
 13. A substantially pure protein characterized by a physiologically active form and comprising an amino acid sequence encoded by the DNA of SEQ ID NO:6.
 14. The protein as in claim 13 having mesoderm differentiation activity.
 15. A composition comprising the protein of claim 13 and a physiologically acceptable carrier with which the protein is admixed. 